Have two sticky pistons facing each other, two blocks apart. Place a slime block between them with the block to duplicate behind it. Place two solid blocks under the sticky pistons and have a one tick delay going from the block under the right sticky piston into the block under the left sticky piston. Have a rapid pulser (such as the one shown in the images where the comparator is in subtraction mode) going into the block under the right sticky piston. Start the pulser and watch as the block gets duplicated and the duplicates get pushed off to either side. The duplicates that are produced are solid blocks but don't give any drops. I think that this works with any solid block but I have only tested dirt and diamond blocks.